These are studies of the pathogenesis and pathologic anatomy of selected virus infections in fetal and suckling laboratoy animals. The major viruses under investigation include parvoviruses, reoviruses, myxoviruses, paramyxoviruses, cytomegaloviruses, adenovirus, and K-virus. Several experimental models of virus-induced developmental defects emerging from these studies include: cerebellar hypoplasia (parvoviruses); aqueductal stenosis and obstructive hydrocephalus (reovirus type 1, mumps virus, parainfluenza type 2 virus); encephalitis with selective neuronitis (reovirus type 3, mumps); encephalitis (cytomegalo-viruses, Newcastle disease virus); adrenalitis (mouse adenovirus); congenital pneumonitis (parainfluenza types 2 and 3 virus), pulmonary endotheliotropism (K-virus). BIBLIOGRAPHIC REFERENCES: Kilham, L. and Margolis, G.: Problems of human concern arising from animal models of intrauterine and neonatal infections due to viruses. A Review. I. Virologic Studies. Progr. in Med. Virol 20:113-143, 1975. Margolis, G. and Kilham, L: Problems of human concern arising from animal models of intrauterine and neonatal infections due to viruses. A Review. II. Pathologic Studies. Progr. in Med. Virol. 20:144-179, 1975.